If you register, you can do a lot more. And become an active part of our growing community. You'll have access to hidden forums, and enjoy the ability of replying and starting conversations.

South African Loco vacuum brakes.

Discussion in 'Locomotive M.I.C.' started by Eightpot, Mar 5, 2016.

  1. Eightpot

    Eightpot Part of the furniture

    Joined:
    Aug 10, 2006
    Messages:
    5,177
    Likes Received:
    618
    Location:
    Aylesbury
    We've got a Class 25NC at Quainton. What puzzles me is why it has two vacuum brake hoses at each end. They are both connected to the same pipework, but no isolation cocks for each hose.

    Can't see any obvious reason for this arrangement, but there must be one. Does anyone know?
     
  2. threelinkdave

    threelinkdave Well-Known Member Friend

    Joined:
    Aug 1, 2013
    Messages:
    1,761
    Likes Received:
    834
    Gender:
    Male
    Occupation:
    Retired
    Location:
    Stratford-upon-Avon or in a brake KD to BH
    Heritage Railway Volunteer:
    Yes I am an active volunteer
    Just a thought, are the hose ends identical. Was there stock with different ends.

    Just had another thought, there is a dummy coupling for each hose? If not did they seal the circuit by conecting both hozes together?
     
  3. Wenlock

    Wenlock Active Member Friend

    Joined:
    Oct 26, 2008
    Messages:
    678
    Likes Received:
    172
    Gender:
    Male
    Occupation:
    Bus Driver
    Location:
    Loughton Essex
    Heritage Railway Volunteer:
    Yes I am an active volunteer
    I seem recall reading somewhere that when Indian railways experimented with very long freight trains they found it necessary to provide two train pipes to be able to get good vacuum at the back. Maybe that was a reason?
     
  4. Eightpot

    Eightpot Part of the furniture

    Joined:
    Aug 10, 2006
    Messages:
    5,177
    Likes Received:
    618
    Location:
    Aylesbury
    Perhaps I did not make myself fully clear. There is only one steel pipe for the vacuum brake going to the loco front and tender back buffer/drawgear beams. Both the flexible hoses are connected to this single pipe, one via a 'Tee' piece, the other via an elbow on the end of the pipe.
     
  5. threelinkdave

    threelinkdave Well-Known Member Friend

    Joined:
    Aug 1, 2013
    Messages:
    1,761
    Likes Received:
    834
    Gender:
    Male
    Occupation:
    Retired
    Location:
    Stratford-upon-Avon or in a brake KD to BH
    Heritage Railway Volunteer:
    Yes I am an active volunteer
    I googled 25NC and there are a number of pics on the web. Intrigingly they only show a single vac pipe. In amoungst the pics is a Garrat which does have two vac pipes.

    Are the hozes still attached or just the swan-necks. Apicture would be interesting

    Dave
     
  6. Wenlock

    Wenlock Active Member Friend

    Joined:
    Oct 26, 2008
    Messages:
    678
    Likes Received:
    172
    Gender:
    Male
    Occupation:
    Bus Driver
    Location:
    Loughton Essex
    Heritage Railway Volunteer:
    Yes I am an active volunteer
    Just found a picture of Quainton's loco, and there is only one vac hose visible on the front end!

    Has someone altered the arrangement since arriving?
     
  7. Eightpot

    Eightpot Part of the furniture

    Joined:
    Aug 10, 2006
    Messages:
    5,177
    Likes Received:
    618
    Location:
    Aylesbury
    Will be going to Quainton this week so should be able to get a photo to put on here.
     
  8. 8126

    8126 Member

    Joined:
    Mar 17, 2014
    Messages:
    457
    Likes Received:
    295
    Gender:
    Male
    As in this linked image?
    I was wondering if they were on opposite sides of the buckeye to facilitate coupling from one side only, but apparently not...
     
  9. Eightpot

    Eightpot Part of the furniture

    Joined:
    Aug 10, 2006
    Messages:
    5,177
    Likes Received:
    618
    Location:
    Aylesbury
    Yes, that's it. But why? There must be a reason for it.
     
  10. Steve

    Steve Resident of Nat Pres Friend

    Joined:
    Oct 7, 2006
    Messages:
    7,980
    Likes Received:
    2,123
    Occupation:
    Gentleman of leisure, nowadays
    Location:
    Near Leeds
    Heritage Railway Volunteer:
    Yes I am an active volunteer
    Just wondering.... what size is the vacuum pipework along the loco? Is it the standard 2". If it is larger, it may be that the vac hoses are 2" because that is standard. Do some SAR wagons/coaches have a similar arrangement? As has been said earlier, propagation of a brake application is dependent on length and diameter and it might be that SAR had 3" pipes on some vehicles, especially passenger vehicles, to provide quicker acting brakes. If a 3" vac hose was provided, it would make the loco incompatible with other stock.
    If it's 2" pipework, I'll shut up !

    Edit:
    More thoughts...Is it possible that some stock has F type cylinders and the second pipe provides the reservoir side? It would need the appropriate non-return valves in the system.
     
    Last edited: Mar 6, 2016
  11. Wenlock

    Wenlock Active Member Friend

    Joined:
    Oct 26, 2008
    Messages:
    678
    Likes Received:
    172
    Gender:
    Male
    Occupation:
    Bus Driver
    Location:
    Loughton Essex
    Heritage Railway Volunteer:
    Yes I am an active volunteer
    I have enlarged a small part of one of my pics, hence the poor quality but it appears to only show one connection. image.jpeg
     
  12. Eightpot

    Eightpot Part of the furniture

    Joined:
    Aug 10, 2006
    Messages:
    5,177
    Likes Received:
    618
    Location:
    Aylesbury
    Correct, only one at the front, but two at the back of the tender. No isolation cocks and normal 2" bore steel vacuum pipe...........
    L1001085.jpg .
     
    Last edited: Mar 7, 2016
  13. Steve

    Steve Resident of Nat Pres Friend

    Joined:
    Oct 7, 2006
    Messages:
    7,980
    Likes Received:
    2,123
    Occupation:
    Gentleman of leisure, nowadays
    Location:
    Near Leeds
    Heritage Railway Volunteer:
    Yes I am an active volunteer
    That's my reasoning down the drain, then!
    Interesting to note that the hose couplings are iron and not aluminium.
     
  14. Grashopper

    Grashopper Member

    Joined:
    Sep 7, 2011
    Messages:
    241
    Likes Received:
    57
    Occupation:
    Assistant FLeet engineer Southern Railway
    Location:
    Surrey
    Heritage Railway Volunteer:
    Yes I am an active volunteer
    Given that they would generally be hauling a load behind the tender, whatever the reason was for this twinning, it can only be surmised that it would not required at the front of the locomotive.
     
  15. odc

    odc Active Member

    Joined:
    Apr 11, 2006
    Messages:
    743
    Likes Received:
    11
    Occupation:
    Network Technician at St Albans School
    Location:
    Hemel Hempstead
    Heritage Railway Volunteer:
    Yes I am an active volunteer
    It is on the front. You can see the blanked off swan neck in the enlarged shot. I have noticed this fenominon several times and spotted only one pipe connected between vehicles and so nullifying the point but never saw the reason why
     
  16. huochemi

    huochemi Active Member Friend

    Joined:
    May 6, 2008
    Messages:
    1,209
    Likes Received:
    353
    Gender:
    Male
    Location:
    UK
    The NBL drawings have two on the tender rear and one on the loco front.
     

Share This Page